Keto Diet Devotees: We’ve Got Some Bad News

Ketogenic diets, usually shortened to keto, are promoted as a way of losing weight and improving your general health, but the long-term impacts of following such a diet are still being unraveled. A new study throws some concerning findings into the mix, suggesting that while the diet may be effective for weight loss, it could lead to complications like fatty liver disease. 

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Keto diets are designed to get the body into a state of ketosis, where fat stores are used as an energy source rather than carbohydrates. To achieve this, these diet plans recommend strict limits on carbohydrate-rich foods, things like starchy vegetables, grains, and sugars. Instead, there’s a focus on protein- and fat-rich foods like meat, fish, unsweetened dairy, nuts, and seeds. 

For some people, a keto diet is an essential part of medical treatment for a chronic illness. For example, ketogenic diet therapy can help children with drug-resistant epilepsy experience fewer seizures. But as the British Dietetic Association points out, following such a strict diet plan comes with its own risks and should be closely monitored. So, what about people without a medical indication who simply choose to follow this diet for themselves?

Lots of people claim the diet has helped them lose weight and feel better, but the internet also abounds with anecdotes from people who claim it ruined their health. The “long-term effects [of ketogenic diets] on metabolic health remain understudied,” write the authors of a new study.

The team, from the University of Utah, kept groups of mice on one of four different diet plans for nearly a year: a low-fat diet, a standard high-fat diet, a ketogenic diet with 89.9 percent fat, and a low-fat diet with higher protein. 

Despite the very high fat content of the keto diet, the mice on this plan did not gain weight in the same way as those on the standard high-fat diet, which would appear to support the idea that keto can support weight loss. 

However, as time progressed, it became clear that the mice on the keto diet were suffering some ill-effects from the plan.

 “[W]hile a [ketogenic diet] can prevent and treat obesity, it causes hyperlipidemia, hepatic steatosis, and glucose intolerance,” the authors write. Hyperlipidemia is an abnormally high level of fats in the blood, which is a major risk factor for cardiovascular disease. Hepatic steatosis, also known as fatty liver disease, can lead to serious liver damage if untreated. 

The liver dysfunction was only observed in male mice, suggesting to the authors that there may be sex-specific differences in how the body responds to this diet. 

Other studies have suggested that keto is best used as a short-term intervention for weight loss and have linked the diet to various negative effects, including heart damage and nutrient deficiencies. Keto has also been compared with other diet plans and found to be lacking, such as a study that found a vegan diet was better for both the environment and health. 

This study was only in mice, so should not be taken as definitive proof that the keto diet will cause these issues in humans. The authors also point out that individual keto diet plans can vary widely, so more research is needed to assess whether tweaks to the diet could help avoid some long-term issues. 

Ultimately, the authors say their results “caution against the systematic use of a [ketogenic diet] as a health promoting dietary intervention.” Decisions about diet are highly personal, but if you’re looking to make a change you should ideally work with a professional such as a registered dietitian to find the balance that’s best for you.

The study is published in the journal Science Advances.